18.5-GHz bandwidth monolithic MSM/MODFET photoreceiver for 1.55-μm wavelength communication systems

A very high-speed, long-wavelength, monolithically integrated photoreceiver front end for optical communication systems is described. The tunable photoreceiver, implemented using a metal-semiconductor-metal (MSM) photodetector and InAlAs-InGaAs-InP modulation-doped field-effect transistor (MODFET)-based transimpedance amplifier, exhibits -3 dB bandwidths of up to 18.5 GHz. The receiver demonstrates a midband responsivity of 178 V/W when tuned for 10 Gb/s operation. Noise measurements revealed an input-referred noise current spectral density of 8 pA/Hz/sup 1/2/ when tuned for 10 Gb/s operation, and 12 pA/Hz/sup 1/2/ when tuned for 20 Gb/s operation. From these noise measurements, sensitivities were calculated to be -16.5 dBm and -12.3 dBm at 10 and 20 Gb/s, respectively, for a bit-error rate of 1/spl times/10/sup -9/. To our knowledge, this is the fastest MSM-based receiver reported to date.